A dielectric ceramic that includes a primarily component and additive components has been disclosed in International Publication No. 2004/067473 pamphlet (Patent Document 1). In this dielectric ceramic, the primary component is a barium titanate-based composite oxide represented by a general formula of (Ba1−h−i−mCahSriGdm)k(Ti1−y−j−nZryHfjMgn)O3, where 0.995≦k≦1.015, 0≦h≦0.03, 0≦i≦0.03, 0.015≦m≦0.035, 0≦y<0.05, 0≦j<0.05, 0≦(y+j)<0.05, and 0.015≦n≦0.035 are satisfied, Ba is partly replaced with Gd, and Ti is partly replaces with Mg. In addition, additive components are Ma (Ma is at least one of Ba, Sr and Ca), Mb (Mb is at least one of Mn and Ni) and Mc (Mc is Si or Si and Ti), in which more than 0 but less than 1.5 moles of Ma is contained with respect to 100 moles of the primary component, more than 0 but less than 1.0 mole of Mb is contained with respect to 100 moles of the primary component, and 0.5 to 2.0 moles of Mc is contained with respect to 100 moles of the primary component.
When dielectric ceramic layers of a multilayer ceramic capacitor are prepared using the above dielectric ceramic, since sintering stability is superior, humidity resistance is improved, the F characteristic specified by the JIS standard and the Y5V characteristic specified by the EIA standard are both satisfied, a relative dielectric constant of 9,000 or more can be obtained, and the multilayer ceramic capacitor can be used in a wide temperature range.
In addition, even when the thickness of the dielectric ceramic layer is decreased, the reduction in size and increase in capacity of the multilayer ceramic capacitor can be realized by decreasing the thickness of the dielectric ceramic layer, and in addition, it is not necessary to decrease the rated voltage since the humidity resistance and the high-temperature reliability are superior. Hence, even when the thickness of the dielectric ceramic layer is decreased, for example, to 3 μm, sufficient practical properties can be imparted to a multilayer ceramic capacitor.
In addition, this dielectric ceramic is not rendered semiconductive and may have a high relative resistance even when fired in a neutral or a reducing atmosphere; hence, when a multilayer ceramic capacitor is formed using this dielectric ceramic, a base metal as a conductive component contained in internal electrodes may be used without causing any problems. As a result, cost of the multilayer ceramic capacitor can be reduced.
However, it was found that in the case in which dielectric ceramic layers of a multilayer ceramic capacitor are formed using the dielectric ceramic disclosed in Patent Document 1 and the thickness of the dielectric ceramic layer is decreased to 2 μm or less, it may become difficult in some cases to ensure the reliability. In addition, in order to sinter the dielectric ceramic disclosed in Patent Document 1, a high firing temperature, such as approximately 1,200° C. or 1,200° C. or more, is required.